Running against Dorothy McDiarmid, a 77-year-old grandmother and member of the Virginia House of Delegates for 22 years, is a bit like trying to dam Niagara Falls.

But Jeanne Morrison, the Republican candidate who hopes to win McDiarmid's seat, insists that her opponent's Democratic philosophy is out of line with that of her constituents -- a factor that Morrison said may be McDiarmid's undoing.

"She's been around for so long and many know her," Morrison said of her opponent, who, if reelected, is expected to chair the powerful House Appropriations Committee as the ranking Democrat.

Morrison, 52, a Republican Party and civic activist, acknowledged that her opponent is influential, but said, "It really boils down to whether you want a lot of power moving in the wrong direction, or less power moving in the right direction."

When McDiarmid, sitting in her Vienna office, heard this assessment, she laughed politely, in a manner befitting a grandmother with a blue-white knot of hair. Then, quickly, as might be expected of the delegate in line to oversee the state's $17 billion biennial budget, she shot back: "It seems to me the only difference between us is that I can be helpful to my district, and she cannot."

"She's a genteel lady with a backbone of steel," Fairfax County Democratic Chairman Pat Watt said of McDiarmid.

"She's probably the only Democrat who could win that district with any degree of regularity," said state Sen. Wiley F. Mitchell Jr. (R-Alexandria).

But Morrison said the time has come for voters in the 35th District, which includes the town of Vienna and the areas of West Falls Church and Dunn Loring, to realize that McDiarmid has voted against many of the issues they are for: the death penalty in murder-for-hire and child murder cases, less government involvement, lower taxes and controlled government spending.

Defending her stance on the death penalty, McDiarmid said: "I am a Quaker, you know . . . . There have been enough cases where executions took place and the person was innocent."

McDiarmid dismissed the charge that she is a proponent of big government and big spending.

"I have been for a balanced budget for years," she said. "And if you know Virginia, its Democratic legislature is one of the most conservative in the country. I work for Virginia."

"I am the average citizen, and sure not a politician," said Morrison, a widowed mother of six. Flipping through past election results in her Falls Church home, she reeled off figures showing that the 35th District voted overwhelmingly Republican in every election but McDiarmid's in recent years.

"I am a Ronald Reagan Republican," she said, pointing to this as the preference of most of the 30,000 voters in her district.

McDiarmid does not mind talking about the two elections since 1959 in which she was defeated by a Republican.

The first time, in 1961, she said, she still was a newcomer in a Republican district, and the second time, on the eve of the election in 1969, President Nixon made a nationally televised plea for Republican votes to help him end the Vietnam War.

Morrison, however, loves to talk about those elections. She sees them as a sign that, although she is spending about $12,000 to McDiarmid's $30,000, voters who head to the polls again with "God, country and families" in mind could make her a winner.

But McDiarmid's is a tough record to beat, Fairfax County Supervisor James M. Scott (D-Providence) said.

"Her name in education is widely known and respected," he said, listing two of her well-known accomplishments: bringing kindergartens to Virginia and spearheading the drive to make George Mason College a degree-granting university with a law school.

"She is clearly one of the most valuable members of the delegation," Scott said. "She is very close to the top."

But Mary Lou Wentzel, the Fairfax County Republican vice chairman, said she agrees with Morrison that it does not matter how much power McDiarmid wields in Richmond if she is not representing her constituents' wishes.

Morrison is going door to door, trying to get the message out that Dorothy McDiarmid is out of sync with her constituents, Wentzel said, adding that, for too long, "Dorothy has been projected as a sweet, little grandmother who has not done any damage down there."

Back at her office, McDiarmid prepared for one of the three daily meetings she attends during the final campaign stretch.

She picked up campaign literature showing how she began her political career more than 35 years ago heading Fairfax County's Parent-Teachers Association, and a newspaper clipping telling how, if reelected, she probably would be the third most powerful state official, behind only the governor and the speaker of the House of Delegates.

"I don't take any election for granted," McDiarmid said. "I always campaign hard."